This invention relates to a vacuum insulating glass (IG) unit, and a method of making the same. More particularly, this invention relates to a vacuum IG unit including a dual peripheral seal (i.e. including two or more seal portions).
Commonly owned U.S. Ser. Nos. 09/303,550 entitled xe2x80x9cVACUUM IG PILLAR WITH DLC COATINGxe2x80x9d filed May 3, 1999, and 09/404,659 filed Sep. 24, 1999 entitled xe2x80x9cVACUUM IG WINDOW UNIT WITH PERIPHERAL SEAL AT LEAST PARTIALLY DIFFUSED AT TEMPERxe2x80x9d, are both hereby incorporated herein by reference.
Vacuum IG units are known in the art. For example, see U.S. Pat. Nos. 5,664,395, 5,657,607, 5,891,536 and 5,902,652, the disclosures of which are all hereby incorporated herein by reference.
Prior art FIGS. 1-2 illustrate a conventional vacuum IG unit. IG unit 1 includes two spaced apart sheets of glass 2 and 3 which enclose an evacuated or low pressure space therebetween. Glass sheets 2 and 3 are interconnected by peripheral or edge seal of rigid fused solder 4 and an array of support pillars 5.
Pump out tube 8 is sealed by solder glass 9 to an aperture or hole 10 which passes from an interior surface of glass sheet 2 to the bottom of recess 11. A vacuum is attached to tube 8 so that the interior cavity between sheets 2 and 3 can be evacuated to create a low pressure area. After evacuation, tube 8 is melted to seal the vacuum. Recess 11 retains melted and sealed tube 8. Chemical getter 12 may optionally be included within machined recess 13.
Conventional vacuum IG units, with their rigid fused solder glass peripheral seals 4, have been manufactured as follows when the upper glass sheet is slightly smaller in dimension than the lower sheet. Solder glass is initially deposited around the periphery of the IG unit in an L-shaped step or corner that is formed by virtue of the upper sheet being slightly smaller in dimension than the lower sheet (not shown in FIGS. 1-2). The entire assembly including sheets 2, 3 and the solder glass seal material is then heated to a temperature of approximately 500xc2x0 C. at which the solder glass melts, wets the surfaces of the glass sheets, and flows into the space between the sheets forming hermetic peripheral seal 4. High temperatures are maintained for from about one to eight hours (it has recently been found that a time of about eight hours including ramping up/down periods is preferred to properly bond solder glass seal material to the glass substrate(s)).
Unfortunately, 500xc2x0 C. temperatures and multi-hour periods over which high temperatures are maintained in forming edge seal 4 are undesirable, especially when it is desired to use a tempered glass sheet in the IG unit. Tempered glass loses temper strength upon exposure to high temperatures as a function of heating time as shown in FIGS. 3-4.
FIG. 3 is a graph illustrating how fully thermally tempered plate glass loses original temper upon exposure to different temperatures for different periods of time, where the original center tension stress is 3,200 MU per inch. The X-axis in FIG. 3 is exponentially representative of time in hours (from 1 to 1,000 hours), while the Y-axis is indicative of the percentage (%) of original tempering strength remaining after exposure. FIG. 4 is a graph similar to FIG. 3, except that the X-axis extends from 0 to 1 hour exponentially. Thus, it would be desirable to use as low of temperature as is reasonable in certain embodiments to form edge seal(s) portion(s). Temper strength remaining would be much improved over certain prior art if temperatures of 450 degrees C. or less could be used following thermal tempering of glass substrate(s).
Solder glass peripheral seal 4 may also be undesirable because of its rigid nature (i.e. easy to break, and if one glass sheet breaks the other sheet likely breaks along with it).
It is apparent from the above that there exists a need in the art for a vacuum IG unit, and corresponding method of making the same, where a hermetic seal may be provided between opposing glass sheets without thermally tempered glass sheet(s) of the unit losing more than about 50% of their original temper strength. There also exists a need in the art for a vacuum IG unit including tempered glass sheets, wherein the peripheral seal is formed such that the glass sheets retain more of their original temper strength than with conventional vacuum IG manufacturing techniques. There also exists a need in the art for a more flexible or ductile peripheral seal portion (as compared to solder glass) for a vacuum IG unit. There also exists a need in the art for a vacuum IG unit peripheral seal which can be formed without having to heat the unit to temperatures as high as those used in conventional solder glass seal units. There also exists a need in the art for a simpler method of forming a vacuum IG peripheral seal(s). It is a purpose of this invention to fulfill any and/or all of the above listed needs in the art.
This invention will now be described with respect to certain embodiments thereof, accompanied by certain illustrations.
An object of this invention is to provide a vacuum insulating glass (IG) unit including a dual peripheral or edge seal.
Another object of this invention is to provide a vacuum IG unit including at least a dual sealing system, wherein a first portion of the seal is flexible and hermetically seals a low pressure space between opposing substrates, and a second portion of the seal is mechanically stronger and less flexible than the first portion of the seal.
Another object of this invention is to form a peripheral seal on a vacuum IG unit by extruding or reaction injection molding (RIM) a polymer-based sealing member onto one or both of the glass substrates (with or without primer therebetween). Such method(s) of seal formation may be more simple than certain prior art methods and/or less costly or time consuming.
Another object of this invention is to provide a vacuum IG unit, wherein thermally tempered glass sheet(s) retain at least about 50% of their original temper strength after formation of the unit.
An object of this invention is to provide an edge or peripheral seal for a vacuum IG unit, wherein the seal does not require processing temperatures greater than about 450xc2x0 C. other than during tempering.
Another object of this invention is to fulfill any and/or all of the above-listed objects.
Generally speaking, this invention fulfills any or all of the above described needs and/or objects by providing a vacuum insulating glass (IG) window unit comprising:
first and second glass substrates;
an array of spacers disposed between said first and second substrates for spacing said substrates from one another so as to define a space therebetween having a pressure less than atmospheric pressure;
a sealing system for sealing said space between said substrates and for bonding said substrates to one another; and
wherein said sealing system includes an inner seal and an outer seal, at least one of said inner seal and said outer seal hermetically sealing said space between said substrates.
This invention further fulfills any or all of the above described needs and/or objects by providing a thermally insulating glass panel comprising:
first and second spaced apart glass substrates defining a low pressure space therebetween having a pressure less than atmospheric pressure;
a plurality of spacers disposed between said first and second glass substrates for spacing said substrates from one another in order to maintain said low pressure space therebetween;
a peripheral seal including at least a flexible inner seal portion and an outer seal portion;
said flexible inner seal portion disposed between said first and second glass substrates for hermetically sealing said low pressure space; and
said outer seal portion bonding said first and second glass substrates to one another, and being less flexible than said inner seal portion.